So far as the origin of androgenic alopecia, many theories are exposited such as (1) imbalance of hormones, (2) genetics, (3) circulatory failure, (4) nutrition.
And it has been also suggested that testosterone (androgenic hormone) played an important role on the generation of hairs.
The theory of Adachi et al which proved the relation between testosterone and androgenic alopecia by biochemical experiments is as follows:
(i) first, testosterone biosynthesized in testis is converted into dihydrotestosterone by 5.alpha.-reductase existed in hair follicle, sebaceous gland etc. at the head.
(ii) dihydrotestosterone reduces the activities of adenyl cyclase remarkably.
(iii) it induces fall of the level of cyclic-AMP in cells.
(iv) last, it induces lowering of energy generation of hairs and the limbus and supressing of protein synthesis (See Biochem. Biophys. Res. Commun., 41, 884 (1970)).
According to the theory it is thought that the results of the series of phenomena, hairs in the growing phase shift to the resting phase, the terminal hairs change to the soft hairs, and the androgenic alopecia develops in the end.
A report by H. V. Schweikert supports this theory that large quantities of metabolites by 5.alpha.-reductase such as dihydrotestosterone etc. in hair follicles of androgenic alopecia-patent exist more than that in females or healthy males. (See J. Clin. Endocr., 38, 811 (1974)).
It was reported that dihydrotestosterone converted from testosterone by 5.alpha.-reductase also plays an important physiological role in the generation of acnes (acne, pimple etc.) other than androgenic alopecia. J. B. Hay et al reported that the metabolism of testosterone by 5.alpha.-reductase was enhanced in the affected part of the skin and the acne aggravated, from the study in the flux between affected skin of acne-patient and healthy skin (See Br. J. Dermatol., 91, 123 (1974)).
G. Sansone et al found that synthetic ability of dihydrotestosterone from testosterone developed from two to twenty times in the affected part of acne-patient compared to that in healthy man, and they suggested that dihydrotestosterone generated by 5.alpha.-reductase greatly relates to the generation or aggravation of acne (See J. Invest. Dermatol., 56, 366 (1971)).
And, dihydrotestosterone is related to the hypertrophy of prostate. Cowan et al reported that large amount of dihydrotestosterone existed in the prostate of prostatic hypertrophy-patient (See J. Steroid Biochemistry, 11, 609 (1979)). Recently, it was known that activity of 5.alpha.-reductase in prostate of prostatic hypertrophy-patient aggravated abnormally (See J. Clinical Endocrinol and Metabolism, 56, 139 (1983)).
From this information it has been clear that dihydrotestosterone also plays an important role in the generation and the development of prostatic hypertrophy.